When you think of a ball screw assembly, you probably envision a screw shaft with a motor connected to one end. The motor turns the screw, and the ball nut travels along the length of the screw shaft. An alternative setup is to hold the screw shaft stationary and rotate, or drive, the ball nut […]
Ball + lead + roller screws
What’s the difference between dynamic load capacity and static load capacity?
Rolling element linear bearings, such as round shafts and bushings, profiled rail guides, crossed roller slides, and even ball screws, have two load capacity specifications — dynamic load capacity and static load capacity — which are based on different operating parameters and performance criteria and are independent of each other. To accurately size and select a […]
When should you lubricate a lead screw?
It’s expected that a ball screw, with metal-on-metal rolling contact between the balls and the raceways, will require periodic lubrication with either grease or oil. One of the advantages that lead screws have over ball screws is that they can often operate without lubrication — eliminating maintenance and the potential hazards that come with using […]
How to calculate the effect of preload on ball screw axial deflection
In a recent post, we looked at the methods for inducing preload in a ball screw assembly and the effects it has on performance. One of those effects is that preload reduces axial deflection (displacement) and increases rigidity. But preload also increases the applied load on the screw assembly and reduces life. To determine the […]
Ball screw preload: What you need to know
When a linear motion application requires high thrust force and rigidity along with good positioning accuracy, a preloaded ball screw assembly is often the best choice. Manufacturers offer ball screw preload amounts ranging from just 1 or 2 percent for applications where backlash would be detrimental, up to 10 percent or greater for applications that […]
Why use a multi-start ball screw?
The easiest way to get higher speed from a ball screw assembly (within the screw’s critical speed limit, which is based on diameter, length, and end fixity) is to use a higher screw lead. But increasing the lead of the screw has a drawback: as the lead increases, the number of effective turns in the […]
Dynatect expands precision ground ball screw capabilities with new end cap ball return design
Replacing precision ground ball screws on legacy equipment is complicated by the dissolving of original manufacturers and by product customizations. Offering multiple types of ball screw return designs provides the flexibility needed to keep older equipment running. The long life of machine tool equipment has resulted in machine tools which are often older than their […]
Ballscrew repair from Dynatect: New calculator to decide when to buy (or refurbish)
Alternatives to the increasing lead time for precision ground ballscrews (PGBS) are driving plant managers to reevaluate procurement options. OEMs often choose to only purchase new precision ground ballscrews (PGBSs) without evaluating repair options. Other choose to maintain no-stock or low-stock of PGBS due to ease of procurement. But now with lead times of 16 to 20 weeks, […]
Lead screw selection: What should I consider besides diameter and lead?
Once you’ve gone through the process of sizing a lead screw, you know what diameter and lead will provide the required load capacity, speed, and back driving torque for the application. But there are hundreds — maybe thousands — of lead screw designs on the market. Beyond the basics of diameter and lead, how do you […]
Lead screw sizing in 4 steps
Lead screw sizing is a bit of a hybrid exercise, with similarities to the process of ball screw sizing, but incorporating some of the considerations that come with sizing a plain bearing. While many factors are involved in the selection of a specific lead screw assembly, lead screw sizing — choosing the right diameter and […]
